The visual system is constantly bombarded with information. The ability to selectively process or attend to a limited portion of this information is necessary to successfully guide behavior. Visual attention can be guided to information that is intrinsically salient (stimulus-driven attention), or to information that matches our current intentions (goal-directed attention). Intermediate to these two varieties of attention is a third type, attentional guidance based on prior experience with a stimulus (memory-guided attention), and in particular, the finding that novelty attracts attention. Relatively little is known about the component processes underlying such novelty-based shifts of attention. The broad aim of the proposed research program is to articulate the neural operations responsible for orienting attention on the basis of memory. Using a newly-developed experimental task and a sophisticated set of multivariate and functional connectivity analysis techniques, we will elucidate how neural signals of short-term plasticity - attenuated responses in ventral visual cortex for stimulus repetitions - guide the orienting of selective visual attention. Three functional magnetic resonance imaging (fMRI) studies will test the relationship between repetition attenuation and shifts of attention toward novel stimuli. The first study will present novel and repeated stimuli concurrently in separate locations, and assess how attenuation for the repeated stimulus influences the allocation of visuospatial attention to the novel stimulus. The second study will present novel and repeated stimuli superimposed at a single location, and assess how attenuation for the repeated stimulus influences the allocation of feature-based attention to the novel stimulus. Finally, the third study will examine how the history of recent stimulus repetitions from a particular category influences the strength of functional connectivity between the corresponding category- selective region of ventral visual cortex and the frontoparietal attention network. Beyond showing that attention influences what we see and remember, these studies will provide evidence for a symmetric relationship, that short-term plasticity in visual cortex can implicitly and dynamically influence the allocation of attention. This research may improve our understanding of how visual cortical plasticity during development and during rehabilitation following injury impacts attentional systems in the brain. PUBLIC HEALTH RELEVANCE: The proposed research will test how short-term plasticity (memory) in visual cortex influences the allocation of selective visual attention. This research may improve our understanding of how visual cortical plasticity during development and during rehabilitation following injury impacts attentional systems in the brain. The tasks that we develop to study memory-guided attention may help clinicians to devise new ways of diagnosing disorders of visual processing.